From reading about subject complement agreement, there seems to be some contention as to whether the complement should be plural or singular. For example, both
“It is a time when teams take a look at their roster and decide whether it’s good enough to be a contender or if it’s time to start rebuilding for next season.”
and
“It is a time when teams take a look at their rosters and decide whether they're good enough to be contenders or if it’s time to start rebuilding for next season.”
seem to be grammatically correct. However, when the sentence is something like
"We have the same computer."
the consensus seems to be that "computer" should remain singular, why is this the case?
Edit: My source for the first two sentences is:https://markallenediting.com/2011/02/19/parts-of-sentences-sometimes-must-agree-to-disagree/, while my final sentence is inspired by posts like these: We have the same car vs we have the same cars